Transnationalism and diaspora are widely-used concepts in academic as well as political discourses. Originally referring to quite different phenomena, today they increasingly overlap. An inflation of meanings goes hand in hand with a danger of essentialising collective identities. This book analyses therefore diaspora and transnationalism as research perspectives rather than as characteristics of particular social groups. The contributions focus on conceptual uses, theoretical challenges, and methodological innovations in the study of social ties that transcend the borders of nations and states. Studying border-crossing affiliations requires also a crossing of disciplinary boundaries. This volume brings together authors from a wide range of fields and approaches in the social sciences